Pulleys are required for guiding and supporting ropes in aerial tramways for the transport of materials and passengers. As shown by EP-A-O 185 531, such pulleys consist of a basic body which has a wheel hub with which the pulley is mounted so as to be rotatable on a fixed spindle. Emanating from the wheel hub are spokes, which are designed as compression spokes and connect the wheel hub to an outer ring of the basic body. This outer ring forms a cylindrical outer circumferential surface, which is defined in the axial direction and thus laterally by two flange disks. The flange disks are a one-piece component of the outer ring.
A tire made of a hard elastomeric material sits in the slot defined in this way, the outer circumferential surface of which tire forms a rope groove. The inner circumferential surface of this tire is a cylindrical surface and has a slightly larger diameter than the slot contained in the outer circumference of the outer pulley ring. A further ring, which is to be elastic, sits in this gap.
The radially outer ring of the rope groove is to be sufficiently wear-resistant, whereas the other, radially inner ring is to produce a certain radial resilience.
However, it has been found here that, in such pulleys, the radial resilience is not sufficient to absorb forces which are produced owing to the fact that a clamping socket acting on the rope runs over the pulley.
The clamping sockets, via which the gondolas hanging on the rope are connected to the rope, constitute local thickening from the point of view of the pulley. When they run over the pulley, on account of the thickening, either the load hanging on the rope must be raised accordingly or the pulley must move downward. This results in considerable forces, since the change in the distance between the center of the pulley and the core of the rope must take place relatively quickly. Even if the pulley as a whole is mounted in an elastic manner, the forces are enormous.
A further problem with such pulleys is the flexing work which the elastomeric material is subjected to during the running. At that location at which the rope rests, the elastomeric tire is compressed and, on account of the rotation of the pulley, this compressed region of the elastomeric tire runs around along the tire, as a result of which flexing work is produced. The flexing work inevitably leads to heating and corresponding wear of the elastomeric tire.